$30,000 to $30 million, or Pricing is all about sourcing

How a $30 Million Renaissance Masterpiece Was Found
A handful of clues tipped off an Italian museum that a painting in its storeroom was a treasure by Mantegna, valued at $30 million, not $30,000

From the comments: 

Yet again the art world loudly proclaims it's hypocrisy.  The value of this painting (and a vast quantity of other 'art') has nothing to due with it's inherent beauty but only with the identity of the creator.  Happily, this is a game only for rich fools and those clever enough to fleece them.

(Note this is from the WSJ and subscription may be required.  Someone noted the Journal has removed access from a Google search.)